DE69910627T2 - FOAM CONTAINING AND EXPANDABLE GRAPHITE BASED ON POLYURETHANE AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

The present invention relates to a process for the production of rigid polyurethane foams containing exfoliating graphite. In a preferred embodiment the foams of the present invention pass severe flame retardant tests such as the M1 burning test. Foams which pass the M1 burning test are produced by reacting a polyisocyanate, a polyol, a halogenated polyol, in the presence of a blowing agent, a catalyst, exfoliating graphite and additional flame retardants selected from phosphonate esters, phosphate esters, halogenated phosphate ester or a combination thereof.

Description

This invention relates to Rigid foam compositions and methods of making such Compositions. In particular, the present invention relates on a combination of flame retardants to make a rigid foam to produce, which has improved flame retardant properties.

Laws have been passed in many countries the standards for the flame protection of materials used in building constructions establish. For example, must polyurethane foams for one Building construction in France the Norme Francaise NF P 92-501, class M1 (M1 test) and in Germany the German standard DIN-4102 part 1, May 1981, building material class B1 (B1 test). To a foam the required degree A large number of attempts have been made to impart flame retardancy.

One approach to rigid foam flame retardants is to add melamine in relatively large amounts. US Patent 4,221,875 describes rigid polyurethane foams that contain melamine powder in one Amount between 20 and 100 parts per hundred parts of the polyhydroxyl compound contain. The European Patent publication 0239891 describes hard polyurethanes which are an alkylene oxide adduct from toluenediamine or diaminodiphenylmethane and an organic Contain polyisocyanate, with melamine as the only flame retardant compound in an amount of at least 5% by weight of the total composition is included.

In the field of flexible foams of expandable (expandable) Graphite reports that it gives the foam flame retardancy. For example, U.S. Patents 4,698,369 and 5,023,280 disclose the Use of graphite in flexible polyurethanes. In flexible Foam graphite is also used in conjunction with other flame retardants. U.S. Patent 5,192,811 describes the use of graphite together with melamine, and from the combination of flame retardants reports that they reduce smoldering or subsequent glow of the foam. U.S. Patent 5,173,515 discloses the use of graphite in one Fire protection element, foaming can be added, the fire protection element graphite, a or more phosphorus-containing polyols and amine salts.

Despite the plethora of procedures disclosed, about flame retardant foams There is still a need to maintain the flame retardancy of foams to improve. Accordingly, It is an object of the present invention to provide a method to produce a flame retardant Rigid foam and / or a plate that has been subjected to serious flame tests, such as the M1 and B1 tests, provide improved performance.

In one aspect, the present Invention a method for producing a rigid polyurethane foam, comprising reacting (1) a polyisocyanate, (2) a polyol, and (3) a halogenated reactive compound, in the presence (4) a blowing agent, (5) a catalyst, (6) expandable graphite, and (7) an additional Flame retardant that selected is from phosphonate esters, phosphate esters, halogenated phosphate esters or a combination thereof.

In another aspect relates the present invention relates to a flame-retardant rigid polyurethane foam-forming Composition comprising a polyisocyanate, a polyol, a halogenated polyol, expandable graphite and additional Flame retardants selected are from phosphonate esters, phosphate esters, halogenated phosphate esters or a combination thereof.

It was surprisingly found that the foams produced by the present process in the Are capable of those mentioned above M1 and B1 tests, as well as a number of other stringent tests such as the A1 test for Italy to exist.

The flame retardant properties of the are foams produced by the present process the result of a unique combination of flame retardants, that work synergistically to provide improved flame retardancy. It is particularly surprising that a small amount of expandable graphite that is added to a polyurethane foam that acts as a fire retardant a reactive halogenated polyol and a phosphate ester, phosphonate ester, contains halogenated phosphate esters or a combination thereof, into one Foam leads, who can pass the strict M1 test. This improvement in fire protection will obtained without adversely affecting the foam properties.

As stated, is an essential one Flame retardant component used in the present invention will, expandable graphite. expandable graphite is graphite, which contains one or more blowing agents, so that when applying heat a considerable one Expansion occurs. expandable graphite is made by methods known in the art, and in general, graphite is first oxidized such as nitrates, chromates, peroxides or by electrolysis to open the Treated crystal layer, and then nitrates or sulfates embedded in the graphite.

Based on the combination of flame retardants disclosed herein, it is possible to use small amounts of graphite in the foam-forming reaction mixture. The amounts of expanded graphite are chosen so that the final foam will pass the M1 test. Generally the amount will be at least 0.5% by weight of the final foam. Advantageously, the amount of graphite used will make up at least 1% by weight of the final foam. Foams containing at least 2% by weight are more preferred. contain graphite. There is no limit to the maximum amount of graphite that can be used, however, because of the particulate nature of the graphite and the increase in viscosity of a graphite-containing polyol, for ease of handling, it is preferred that the graphite be used in an amount that is less than 10% by weight of the final foam. The amount of graphite is preferably less than 9% by weight of the final foam. More preferably, graphite makes up less than 6.5% by weight of the final foam. Most preferred are foams containing 5 wt% or less graphite.

A second flame retardant, the used in the present invention is a reactive one halogenated compound. Such connections are considered reactive referred to as they generally become part of the polymer. This reactive compounds generally contain halogen units and also contain one or more reactive groups such as -OH or -COOH, which can react with an isocyanate unit. Such Compounds are known in the art, and are general halogenated polyols such as derivatives of phthalic acid, bisphenol A, an anhydride or an alcohol. For example, U.S. Patents 4,072,638; 4,067,911 and 4,173,710 halogenated polyether polyols. Examples such reactive halogenated compounds include diesters / ether diol of tetrabromophthalic anhydride, Tetrabromobisphenol A, IXOL B251 (a halogenated polyether polyol available by Solvay S.A.), tetrabromobisphenol A bis (allyl ether), tetrabromobisphenol A bis (2-hydroxyethyl ether); Tribromophenyl maleimide, tetrabromophthalate, dibromopentyl glycol, Tetrabromodipentaerythritol, tetrabromophthalic anhydride, dibromopropanol, Het-acid and tetrachlorophthalic anhydride on. The halogen is preferably bromine.

The amount of reactive halogenated Compound used in the present invention generally less than 5% of the total polyol component of the Foam mixture. Preferably, the reactive halogenated compound less than 40% of the total polyol component, and more preferred 30% by weight or less of the total polyol component. It is generally known in the art that polyurethane foams that pass the M1 test, can be made if a halogenated Polyol is used, the halogenated polyol being more than 70% or more of the polyol present. Because the halogenated Polyols are generally more expensive and more difficult than conventional polyols are manageable during processing, reducing the amount of halogenated Polyols required in the present invention, the Total cost of the foam components and easier processing.

Additional flame retardants which are used in the present invention are selected from Phosphonate esters, phosphate esters, halogenated phosphate esters or a combination of these.

Phosphonate esters for use in of the present invention by the formula R-P (O) (OR ') (OR' '), where R, R' and R '' are each independently are an alkane having 1 to 4 carbon atoms. Preferred compounds of this group are dimethyl methyl phosphonate (DMMP) and diethyl ethyl phosphonate (DEEP).

Phosphate esters described in the present Invention can be used are trialkyl phosphates such as triethyl phosphate and tricresyl phosphate.

When used, they are Phosphonate or phosphate ester flame retardants in the final foam in an amount of 0.5 to 10% by weight of the final foam available. They preferably make up 1 to 8.5% by weight of the final foam out. More preferably they make up 2 to 6.5% by weight of the final foam.

Halogenated phosphate esters associated with fire protection are known in the art and can be represented by the general formula P (O) (OR'X ' _n ) (OR''X'' _n ) (OR''' X ''' _n ), where R ', R''andR''' are each independently an alkane with 1 to 4 carbon atoms, X ', X''andX''' are each independently a halogen and n is an integer from 1 to 3 is shown.

Examples of halogenated phosphate esters include 2-chloroethanol phosphate (C ₆ H ₁₂ Cl ₂ O ₄ P); 1-chloro-2-propanol phosphate [tris (1-chloro-2-propyl) phosphate] (C ₉ H ₁₈ Cl ₃ O ₄ P) (TCPP); 1,3-dichloro-2-propanol phosphate (C ₉ H ₁₅ Cl ₆ O ₄ P), also called tris (1,3-dichloro-2-propyl) phosphate; Tri (2-chloroethyl) phosphate; Tri (2,2-dichloroisopropyl) phosphate; Tri (2,3-dibromopropyl) phosphate; Tri phosphate (1,3-dichloropropyl); Tetrakis (2-chloroethyl) ethylene diphosphate; Bis (2-chloroethyl) 2-chloroethylphosphonate; Diphosphate [2-chlorethyldiphosphat]; Tetrakis (2-chloroethyl) ethylene diphosphate; Tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tetrakis (2-chloroethyl) ethylene diphosphate and tetrakis (2-chloroethyl) ethyleneoxyethylene diphosphate.

Tribromoneopentylchloroalkylphosphate, as in EP 0 735 039 have the formula [(BrCH ₂ ) ₃ C-CH ₂ )] _m PO (OCYHCH ₂ Cl) _3-m , where Y is hydrogen, an alkyl having 1 to 3 carbon atoms or a chloroalkyl group and m is 0.95 to 1.15, and can also be used.

When used as a flame retardant the halogenated phosphate esters are at least 1 wt .-% make up the final foam, preferably at least 2% by weight of the final foam and more preferably at least 4.5% by weight of the final foam. The halogenated Phosphate ester exceeds generally not 9% by weight of the final foam, preferably 8% or less of the final foam and more preferably less than 6.5% by weight of the foam.

In a preferred embodiment of the present invention, those for producing Rigid foams of the present invention have used the use of expandable graphite, a halogenated reactive polyol and a combination of a phosphonate ester or phosphate ester and halogenated phosphate ester.

The polyisocyanates, polyols, the Catalyst and blowing agent for the production of rigid foams The present invention are those that are well known in the art are and ordinary be used.

Polyisocyanates used in manufacturing of polyurethanes useful are close aliphatic and cycloaliphatic and preferably aromatic Polyisocyanates or combinations thereof, preferably with one average value from 2 to 3.5 and preferably from 2.4 to 3.2 isocyanate groups per molecule. During execution raw polyisocyanate can also be used in this invention, such as crude toluene diisocyanate obtained by phosgenating a mixture is obtained from toluenediamine, or the crude diphenylmethane diisocyanate, obtained by phosgenation of crude methylenediphenylamine becomes. The preferred polyisocyanates are aromatic polyisocyanates, as disclosed in U.S. Patent 3,215,652. Because of their ability Crosslinking the polyurethane are methylene-bridged polyphenyl polyisocyanates and mixtures thereof with crude diphenylmethane diisocyanate in particular prefers.

The amount of polyisocyanate present in the production of the polyurethane foam is such that from 0.6 up to 3.0 isocyanate groups per isocyanate-reactive atom contained in the / the Polyol (s) and any water that may be present to be provided. Preferably the amount of isocyanate is such that 0.7 to 2 isocyanate groups per isocyanate-reactive atom, which in the polyol (s) and any water that may be present is available. The amount is more preferred of isocyanate 0.8 to 1.6 isocyanate groups per isocyanate-reactive Atom that is in the polyol (s) and any water that is present can be present. If the same ratio as a multiple of 100 is expressed this is called the isocyanate index.

Polyols used in manufacturing of polyisocyanate-based cellular polymers are appropriate include those Materials that have two or more groups that have an active one Contain hydrogen atom, which is a reaction with an isocyanate can come in. Preferred such compounds are materials the at least 2 hydroxyl, primary or secondary Amine, carboxylic acid, or thiol groups per molecule contain. Compounds with at least 2 hydroxyl groups per molecule are due your desired Reactivity particularly preferred with polyisocyanates. Typical polyols that are suitable for the production of hard polyurethanes, include such one that is an equivalent weight from 30 to 700, preferably 70 to 300 and more preferably 70 to Own 150. Such polyols preferably have a functionality of at least 2, preferably 3 and up to 6, preferably up to 8, active hydrogen atoms per molecule. representatives of polyols Polyether polyols, polyester polyols, polyhydroxy-terminated acetal resins, Hydroxyl-terminated amines and polyamines. Examples of this and other suitable isocyanate-reactive materials are more complete in U.S. Patent 4,394,491. Preferred for the production of rigid foams The performance characteristics, availability and costs are the basis a polyol obtained by adding an alkylene oxide to an initiator with 2 to 8, preferably 3 to 8 active hydrogen atoms becomes. Examples of such polyols include those listed under the Product name VORANOL including VORANOL 280, VORANOL 360, VORANOL 370, VORANOL 446, VORANOL 490, VORANOL 575, VORANOL 800, all of which are sold by The Dow Chemical Company, commercially available are. Other highly preferred polyols include alkylene oxide derivatives of Mannich condensates as they are e.g. For example, in U.S. Patents 3,297,597; 4,137,265 and 4,383,102; and aminoalkypiperazine-initiated Polyethers as described in U.S. Patents 4,704,410 and 4,704,411 are.

In a preferred embodiment In this invention, the polyol is a composition comprising a Sugar-initiated (like sucrose) polyether polyol with 30 to 90 Parts per 100 parts of the total weight of the polyol composition. additionally the composition can be added to the sugar-initiated polyether polyol also a sorbitol initiated polyol, an amine initiated polyether polyol and water-initiated polyether polyol, each with 3 to 35 parts per 100 parts of the total weight of the polyol composition. In a highly preferred embodiment of this invention the polyol composition is a sugar initiated polyol of 30 to 90 parts; a sorbitol (sorbital) initiated polyol with 3 to 35 parts, an amine initiated polyether polyol of 3 to 35 parts; a water-initiated polyol with 5 to 35 parts and a halogenated reactive polyol with 20 to 40 parts per 100 parts of the total weight the polyol composition.

Because of the fire protection properties associated with aromatics-initiated polyols, the polyol used in another preferred embodiment contains an aromatics-initiated polyether polyol with 20 to 70 parts per 100 parts of the total weight of the polyol compositions. In addition to the polyols described above, the composition can also be an amine-initiated polyether polyol at 5 to 35 parts per 100 parts of the total weight of the composition; or alternatively, contain an aromatic polyester polyol that is liquid at room temperature with 5 to 35 parts per 100 parts of the total weight of the composition. Advantageously, the aromatic-initiated polyether polyol is an alkylene oxide adduct of a phenol / formaldehyde resin, often referred to as "Novolac" polyol, as described in US Pat tenten 3,470,118 and 4,046,721, or an alkylene oxide adduct of a phenol / formaldehyde / alkanolamine resin, often referred to as "Mannich" polyol, as described in U.S. Patents 4,883,826; 4,939,182 and 5,120,815.

When a rigid foam is made, a blowing agent is present. The blowing agent is present in an amount such that the foam is provided with the desired overall density. Typically a density of 25 to 60, preferably 30 to 55 and more preferably 35 to 50 kg / m ^{3 is} desirable.

Generally the rigid foams are these Invention predominantly closed cell and it is preferred that a halocarbon blowing agent is the main part of the blowing agent accounts for the fact that such blowing agents have additional thermal insulation properties provide. Such blowing agents can be fully or partially halogenated be aliphatic hydrocarbons and include fluorocarbons, chlorocarbons and chlorofluorocarbons. Examples of fluorocarbons include methyl fluoride, Perfluoromethane, ethyl fluoride, 1,1-difluoroethane, 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), pentafluoroethane, difluoromethane, Perfluoroethane, 2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, Perfluorobutane, perfluorocyclobutane.

Partially halogenated chlorinated carbons and chlorofluorocarbons for use in this invention include methyl chloride, Methylene chloride, ethyl chloride, 1,1,1-trichloroethane, 1,1-dichloro-1-fluoroethane (FCFC-141b), 1-chloro-1-1,1-difluoroethane (HCFC-142b), 1,1-dichloro-2,2,2-trifluoroethane (HCHC-123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) a.

Fully halogenated chlorofluorocarbons conclude Trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), Trichlorotrifluoroethane (CFC-113), 1,1,1-trifluoroethane, pentafluoroethane, dichlorotetrafluoroethane (CFC-114), chlorheptafluoropropane and dichlorohexafluoropropane. The halocarbon blowing agent can together with low-boiling hydrocarbons such as butane, pentane (including of the isomers thereof), hexane or cyclohexane or with water become.

If water as an additional Propellant is present, it is generally in an amount from 0.5 to 10, preferably from 0.8 to 6 and more preferably from 1 to 4 and most preferably 1 to 3 parts of the total weight of the total polyol composition present. Water acts as Blowing agent because water reacts with isocyanate, leading to the formation of Carbon dioxide leads.

In addition to the previous ones critical components, it is often desirable to have certain other components in making cellular To use polymers. Among these additional ingredients are catalysts, surfactants Agents, preservatives, dyes, antioxidants, reinforcing agents, stabilizers and filler. In general, when making a polyurethane foam highly preferred, a smaller amount of a surfactant Means to use the foaming Stabilize the reaction mixture until it solidifies. Such surface active Agents preferably comprise a liquid or solid organosilicone surfactant Medium. Other less preferred surfactants include polyethylene glycol ethers long chain alcohols, tertiary Amine or alkanolamine salts of long-chain alkyl acid sulfate esters, alkyl sulfonic acid esters and alkylarylsulfonic acids on. Such surface active Agents are used in amounts sufficient to control the foaming reaction mixture across from to stabilize a collapse and the formation of large, uneven cells. Typically, 0.2 to 3 parts of the surfactant per 100 Parts by weight of polyol are sufficient for this purpose.

Be advantageous for implementation the polyol (and water, if present) with the polyisocyanate one or more catalysts used. Any suitable Urethane catalyst can be used, including tertiary amine compounds and organometallic Links. Examples of tertiary Close amine compounds Triethylenediamine, N-methylmorpholine, N, N-dimethylcyclohexylamine, pentamethyldiethylenetriamine, Tetramethylethylenediamine, 1-methyl-4-dimethylaminoethylpiperazine, 3-methoxy-N-dimethylpropylamine, N-ethylmorpholine, diethylethanolamine, N-cocomorpholine, N, N-dimethyl-N'N'-dimethylisopropylpropylenediamine, N, N-diethyl-3-diethylaminopropylamine and dimethylbenzylamine. Examples of organometallic catalysts conclude Organo-mercury, organo-lead, organo-iron and organotin catalysts one, organotin catalysts thereof being preferred. suitable Tin catalysts close Tin chloride, tin salts of carboxylic acids such as dibutyltin dilaurate as well as other organometallic compounds as described in the US patent 2,846,408. Possibly. can also be a catalyst herein for the Trimerization of polyisocyanates are used, resulting in a Polyisocyanurate leads, such as B. an alkali metal alkoxide. Such catalysts are used in an amount used which is the rate of polyurethane or polyisocyanurate formation noticeably increased. Typical amounts are 0.001 to 3 parts of catalyst per 100 parts by weight of the entire polyol.

The hard polyurethanes of the present invention are readily made according to standard procedures in the art in which the polyisocyanate, the active hydrogen-containing material, the blowing agent and other foam-forming ingredients, including the expandable graphite and other flame retardants, are at a temperature from 10 ° C to 80 ° C are brought together under foam-forming conditions. Any order of mixing is acceptable and expandable graphite is preferred homogeneously mixed into the foam-forming formulation. In a preferred embodiment, the expandable graphite is homogeneously dispersed in the polyol component. The expandable graphite dispersion in polyol can be added as a concentrate of the polyol composition via a separate line on the mixing head.

In general, the rigid foams are through discontinuous or continuous processes, including the Process called the discontinuous plate process (DCPP, Discontinuous Panel Process) and that as a double barrier laminate (Double Ban Laminates, DBL) is called the foaming reaction and the subsequent hardening in molds or in conveyors be performed. If the foams used in laminates, the layer can be flexible, e.g. As aluminum foil or coated paper, or can be from one rigid material such as a plasterboard, polyester surface or steel surface getting produced. Other methods of making construction foams are as spray and block foams known.

The rigid foams of the present invention are closed-cell foams. With closed-cell foams means that at least 75%, preferably 80% or more and more preferably 85% or more of the cells are closed. In a preferred embodiment 90% or more of the cells are closed. Because of the closed cell Structures become the rigid polyurethane foams of the present invention for thermal Insulation applications such as roofing material, cladding and in-situ spraying applications used.

The following examples are given to illustrate the invention and should not be construed as being on any Restricting way be considered. Unless otherwise stated, all are Parts and percentages by weight.

EXAMPLES

A description of the raw materials used in the examples is as follows: DEEP was the flame retardant additive diethyl ethyl phosphate TCPP was the flame retardant additive tris (1-chloro-2-propyl) phosphate TEGOSTAB B8462 was a silicone based surfactant available from Th. Goldschmidt Chemical Corporation. DMCHA was JEFFCAT DMCHA, an N, N-dimethylcyclohexylamine catalyst available from Huntsman Corporation. Niax DMEE was an amine based catalyst available from OSI Specialties-Witco. Curithane 52 was an organic salt catalyst available from The Dow Chemical Company. Allocimene was a UV (light) stabilizer available from Les Derives Resiniques & Terpeniques. PREVIOUS M220 was a polymeric isocyanate available from The Dow Chemical Company. (VORANATE is a trademark of The Dow Chemical Company).

The expandable graphite used in the examples was S15-PU120, available from Ajay Metachem, India. Polyol A VORANOL RN490, a glycerin / sucrose initiated polyoxypropylene polyether polyol having a hydroxyl number of 490 and an equivalent weight of 114, available from The Dow Chemical Company. Polyol B VORANOL RN482, a sorbitol initiated polyoxypropylene polyether polyol having a hydroxyl number of 482 and an average equivalent weight of 117, available from The Dow Chemical Company. Polyol C VORANOL RA640, an ethylenediamine initiated polyoxypropylene polyol with a hydroxyl number of 640 and an average equivalent weight of 88, available from The Dow Chemical Company. Polyol D VORANOL P1010, was a water initiated polyoxypropylene polyether polyol having a hydroxyl number of 110 and an average equivalent weight of 510, available from The Dow Chemical Company. Saytex RB-79 was a dietherdiol of tetrabromophthalate anhydride available from Ethyl Corp.

A base polyol blend was made by mixing the following ingredients, in parts by weight were: 30.5 polyol A; 5 polyol B; 4 polyol C; 6.7 polyol D; 18 Syatex RB-79; 10 DEEP; 12.6 TCCP; 1.2 Tegostab B 8462; 2.1 water; 0.7 DMCHA; 0.5 Niax DMEE; 0.6 Curithane 52 and 0.1 Allocimene.

The base polyol, graphite, became a container and the blowing agent was added, then the mixture was stirred gently The amount of blowing agent was adjusted to compensate for the evaporation and then the isocyanate was added. The mixture was then for Stirred for 10 seconds at 3000 rpm, before pouring the mixture into a preheated mold at 60 ° C has been. In the mold there was a steel layer (30 × 40 mm) on which the mixture was poured. After 45 min the sample was removed from the Form removed. They were left Samples about Stand night, and then they were cut for testing. The characteristic Properties of the foam in the presence of different amounts of graphite are given in Table 1.

Table I

To pass the B2 test was one Flame less than 15 cm is required. To pass the M1 test a value less than 2.5 was required.

The results show that the addition of 4.6% by weight graphite to the total foam composition led, that the foam produced is both the B2 and the M1 test happened. The results with the slight addition of expandable graphite show that the flame retardant properties of the foam are similar to those which were obtained when 30% by weight of expandable graphite was added to the polyol formulation were. Formulations containing the added graphite but not the reactive halogenated compound or the phosphonate or contained phosphate ester or a chlorinated phosphate ester, led to a foam that failed the M1 test.

It is within the expertise in the art, the invention in view of the above teaching in numerous To carry out modifications and variations. It is therefore to be understood that different embodiments of this invention described herein can, without departing from the spirit and scope of this invention, as by the pending Expectations defined, deviated.

Claims (18)

Process for the production of a rigid polyurethane foam, comprehensively implementing (1) a polyisocyanate, (2) one Polyols, and (3) a halogenated reactive compound, which is a halogenated polyol in present (4) one Propellant, (5) a catalyst, (6) expandable graphite, and (7) an additional Flame retardant that selected is from phosphonate esters, phosphate esters, halogenated phosphate esters or a combination thereof. The method of claim 1, wherein the foam is a closed cell Rigid polyurethane foam is. The method of claim 2, wherein the halogenated reactive compound is a halogenated polyol and less than 50% by weight, preferably less than 30% by weight of the total polyol accounts. Method according to one of the preceding claims, wherein the polyol (2) is a polyether polyol. Method according to one of claims 1 to 3, wherein the polyol (2) is a polyester polyol. The method of claim 4 or 5, wherein the polyol is an aromatic polyol. The method of claim 6, wherein the polyol is a molecular weight from 400 to 2000 and has a functionality from 2 to 8. The method of claim 1, wherein the additional Flame retardants (7) are present in such an amount that they make up 1 to 20% by weight of the final foam. The method of claim 8, wherein the additional Flame retardants at least one phosphonate ester and at least contain a halogenated phosphate ester. The method of claim 9, wherein the phosphonate ester and halogenated phosphate esters are each present in such an amount are that they make up 0.5 to 10% by weight of the final foam. The method of claim 10, wherein the phosphonate ester is present in an amount such that it contains 1 to 8.5% by weight of the End foam and the halogenated phosphate ester in one is present in such an amount that it contains 2 to 8% by weight of the final foam accounts. The method of claim 1, wherein the graphite in is present in such an amount that it is at least 0.5% by weight of the final foam. Flame retardant rigid polyurethane foam A composition comprising a polyisocyanate, a polyol, a halogenated Polyol, expandable graphite and additional Flame retardants that are selected from phosphonate esters, phosphate esters, halogenated phosphate esters or a combination thereof. The composition of claim 13, wherein the halogenated Polyol makes up less than 50 percent of the total polyol present. The composition of claim 13 or 14, wherein the graphite makes up at least 2% by weight of the composition. The composition of claim 15, wherein the composition 2 to 10% by weight of a phosphonate ester and 2 to 10% by weight of one contains halogenated phosphate esters. Rigid polyurethane foam made from the composition is formed according to claim 16. Rigid polyurethane foam formed by the process according to one of the claims 1 to 12.